Hey Bubba...I’ve hunted 5 different fairgrounds. I’m assuming yours is old and has history? Like at least 100 years? If so,I can tell you this...EVERYBODY has hunted and STILL hunts these fairgrounds! You might not think so,but they do. I have found one common denominator in these places. There ARE coins! ALOT of them! The problem is that with all of the trash that has accumulated over time,the ones under all that trash are hard to find! The really old fairgrounds have had millions of nails deposited everywhere,that’s how stuff was put together back in the day. I know you know this but perhaps you under-estimate how many rotten wooden things have mulched into these places,with only nails remaining! All of the coil wrappers,pop caps,twist offs,pull tabs....you need the SMALLEST coil you have attached to the machine you know best. Hunt the edges of the roads and paths that go through and around the fairground....basically where people WALKED. if you know where they parked,look there also.
If it has age,it has coins. All the easy ones are simply gone,for the very great part.
This is just what I’ve experienced,hopefully you can make another run at it with some success!